CN111377833A - Preparation method of AC foaming agent - Google Patents
Preparation method of AC foaming agent Download PDFInfo
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- CN111377833A CN111377833A CN201811644128.6A CN201811644128A CN111377833A CN 111377833 A CN111377833 A CN 111377833A CN 201811644128 A CN201811644128 A CN 201811644128A CN 111377833 A CN111377833 A CN 111377833A
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- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C281/00—Derivatives of carbonic acid containing functional groups covered by groups C07C269/00 - C07C279/00 in which at least one nitrogen atom of these functional groups is further bound to another nitrogen atom not being part of a nitro or nitroso group
- C07C281/20—Derivatives of carbonic acid containing functional groups covered by groups C07C269/00 - C07C279/00 in which at least one nitrogen atom of these functional groups is further bound to another nitrogen atom not being part of a nitro or nitroso group the two nitrogen atoms of the functional groups being doubly-bound to each other, e.g. azoformamide
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Abstract
The invention relates to a preparation method of an AC foaming agent, which uses a jet reaction device to intensively mix part of biurea slurry and chlorine to react instantly to generate AC foaming agent crystal nuclei, then adds the crystal nuclei into the rest of biurea slurry, and adds an oxidant to oxidize to generate the AC foaming agent. The process has the advantages that the particle size and the particle size distribution range of the AC foaming agent can be controlled, the use stability of the AC foaming agent is favorably improved, and the added value and the market competitiveness of products are improved.
Description
Technical Field
The invention relates to the technical field of AC foaming agents, in particular to a preparation method of an AC foaming agent.
Background
The AC (azodicarbonamide) foaming agent can be decomposed to generate a large amount of gas in a very narrow temperature range and a very short time, and the generated gas and residues are non-toxic, odorless, pollution-free, non-coloring, non-corrosive to processing equipment, free from influencing the mechanical property and stability of products, good in dispersibility in plastics and rubber, and fine and uniform in formed cells, and is the organic foaming agent with the widest application range in the world.
An important index for measuring the quality of the AC foaming agent product is the particle size and the distribution state of the product, the existing product has the phenomenon of wide and irregular particle size distribution, and the too wide particle size distribution of the AC foaming agent causes a lot of difficulties for the foaming process. The small-particle-size AC foaming agent has large specific surface area, strong activity and short decomposition process, and is likely to foam in advance, so that the defective products and the rejection rate of the foamed products are high. The large-particle-size AC foaming agent has small specific surface area, weak activity and long decomposition process, and tends to delay foaming or even not foam, so that the surface of a foamed product is yellowed, and the color and the quality of the foamed product are seriously influenced. Therefore, it is highly desirable for blowing agent manufacturers to have the particle size distribution of the blowing agent as narrow as possible, i.e., to have the particle size distribution of the blowing agent as uniform as possible.
Most of products sold in China and export are foaming agent AC raw powder, the variety is single, the characteristics of rough product particle surface, wide particle size distribution range and the like exist, the product addition is low, the selling price is lower than that of foreign countries, and the market demand cannot be met. Therefore, the research and development of a new process technology to change the backward appearance of the single variety of the foaming agent AC in China so as to increase the variety of colors and meet the market demands of various users, improve the product quality, and improve the added value and the market competitiveness of the product are necessary and urgent.
Disclosure of Invention
The invention aims to solve the defects in the prior art, and provides a method for regulating and controlling the particle size of an AC foaming agent, so that the product quality and the added value of the AC foaming agent are improved, and the market competitiveness and the economic benefit of the product are improved.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a preparation method of an AC foaming agent comprises the following steps:
(1) crushing the biurea raw material: filtering and washing the synthesized biurea, and performing superfine grinding on the biurea to obtain particles with the particle size of 4-8 mu m;
(2) preparation of biurea slurry: adding water into the crushed biurea to prepare a biurea slurry containing 20-40% of biurea, and then adding an oxidation auxiliary agent with the mass ratio of 0.3-10% of biurea;
(3) generating seed crystals: spraying the prepared 3-10% biurea slurry at a high speed through a liquid spraying device, entering the spraying reaction device from one inlet of the spraying reaction device, forming vacuum in the spraying reaction device, sucking chlorine gas into the spraying reaction device from the other inlet of the spraying reaction device, violently mixing the two in the spraying reaction device to instantly form a large amount of AC foaming agent crystal seeds, and collecting a reaction mixture with the AC foaming agent crystal seeds;
(4) mixing uniformly: adding the rest biurea slurry and the generated AC foaming agent seed crystal into a reaction kettle provided with a gas disperser, adding a crystal form control agent, and uniformly mixing;
(5) adding an oxidant and continuing oxidizing until the reaction is finished;
(6) washing and drying: and after the reaction is finished, separating, washing and drying the slurry to obtain the finished product of the AC foaming agent.
Further, the oxidant in the step (5) is chlorine, and the flow of the chlorine at the early stage is controlled to be 0.8-1.2 m3The flow rate of chlorine gas in the middle period is 2.1-2.8 m3The flow rate of chlorine gas is 0.8-1.2 m in the later period3/min。
Further, the oxidant in the step (5) is hydrogen peroxide and chlorine.
Further, the step (5) comprises the steps of:
introducing chlorine gas into the reaction kettle to reach 85% -95% of theoretical chlorine flow, dropwise adding hydrogen peroxide to continue oxidizing until the reaction is finished, and controlling the early chlorine flow to be 0.8-1.2 m3The flow rate of chlorine gas in the middle period is 2.1-2.8 m3The flow rate of chlorine gas is 0.8-1.2 m in the later period3/min。
Further, the step (5) comprises the steps of:
simultaneously introducing chlorine and dropwise adding hydrogen peroxide, wherein the mole ratio of the introduced chlorine to the introduced hydrogen peroxide is (1.1-1.2): (1-1.05) and the chlorine flow rate at the early stage is controlled to be 0.8-1.2 m3The flow rate of chlorine gas in the middle period is 2.1-2.8 m3The flow rate of chlorine gas is 0.8-1.2 m in the later period3And/min until the reaction is finished.
Further, the crystal form control agent is urotropin.
Further, the gas disperser comprises a gas inlet pipe, a bottom plate, a side wall and a cover plate; the bottom plate, the side wall and the cover plate are fixedly connected to form a cavity; one end of the air inlet pipe is communicated with the cover plate; the cover plate is conical, and vent holes are uniformly formed in the cover plate.
Furthermore, an included angle α is formed between the cover plate and the side wall, and the size of the α is 90-120 degrees.
Furthermore, an impeller is sleeved on the air inlet pipe in a hollow mode and can rotate in the radial direction.
Further, a clutch is arranged at the bottom of the reaction kettle, the clutch can enable the impeller and the gas disperser to rotate at the same speed or the gas disperser to rotate independently, and the impeller is driven by water flow to rotate at a low speed.
Furthermore, the injection reaction device is provided with a spray head, an injection pipe and a reaction chamber, an outlet of the spray head is connected with one end of the injection pipe, the other end of the injection pipe is connected with the accommodating chamber, the spray head is provided with two inlets, the biurea slurry enters the spray head from one inlet, and the oxidant enters the spray head from the other inlet.
The technical scheme has the advantages that:
1. in the prior art, the synthesis of biurea is basically carried out in a reaction kettle, the particle size of the obtained biurea is basically between 40 and 160 mu m, if the biurea enters the stage of producing the AC foaming agent by oxidation without treatment, the dissolution speed of crude biurea in a solution is low, the dissolution speed of the crude biurea is inconsistent with the reaction speed of oxides due to inconsistent particle sizes, the overall reaction speed is low, the particle size range of the obtained AC foaming agent product is wide and inconsistent, if the crude biurea is subjected to superfine treatment before reaction, the particle size of the treated biurea is small, the particle size uniformity is high, the dissolution rate is high, the overall reaction speed is high, the particle size of the AC foaming agent is easy to control, and the particle size distribution range is narrow. In the preparation method of the AC foaming agent provided by the invention, the biurea is crushed in advance before being oxidized by chlorine, the specific surface area is increased, the dissolving speed of the biurea is higher in the reaction process, and the dissolving speed of the biurea is improved, so that the particle size of the AC foaming agent product is favorably controlled.
2. The AC foaming agent is added in advance as a seed crystal before the biurea is oxidized to prepare the AC foaming agent, then the oxidant is added to carry out the oxidation reaction of the biurea, the nucleation and the crystal growth of the AC foaming agent are carried out separately, the defects of wide particle size distribution, poor dispersibility and easy agglomeration of the AC foaming agent caused by different growth periods of the AC foaming agent can be avoided, and the AC foaming agent with narrow particle size range and uniform particle size can be obtained.
3. The biurea and the chlorine can be mixed vigorously by adopting the spray reaction device and react instantly to form a large amount of AC foaming agent crystal nuclei, the reaction time is short, the growth of crystals can be inhibited, and the biurea is continuously sprayed out by the liquid spray device, so that the generated AC foaming agent crystal nuclei are uniform and stable.
4. The method has the advantages that the chlorine is used for oxidation in the early stage of the reaction, the cost is low, the reaction speed is high, but the chlorine oxidation is not easy to control the reaction end point, the side reaction is easy to occur, the byproduct hydrochloric acid can be generated, the concentration of the hydrochloric acid is gradually increased along with the reaction, the color of the product is dark, the purity is low, the hydrogen peroxide is used in the later stage of the reaction, the reaction is changed from gas-liquid-solid three-phase reaction to liquid-solid two-phase reaction, the reaction is more sufficient, the reaction is mainly easy to control, the peroxidation phenomenon of the AC foaming agent after the reaction.
5. The reaction of oxidizing the biurea by the chlorine gas can generate a large amount of hydrochloric acid as a byproduct, the oxidizing of the biurea by the hydrogen peroxide needs to be carried out in an acidic environment, the concentration of the hydrochloric acid is reduced along with the proceeding of the oxidizing reaction of the hydrogen peroxide, the difficulty of later oxidation is increased, and the yield and the purity of the product are low.
6. The crystal form control agent is added to adjust the particle size of the AC foaming agent, and the finished product of the AC foaming agent is prevented from being granulated and agglomerated, so that the particle size of the AC foaming agent product is favorably controlled. When the crystal form control agent urotropine is used as an auxiliary agent in a chemical reaction process, solid particles can be effectively wrapped, and organic matters can have a dispersion characteristic, so that when biurea is oxidized by adopting an oxidant, the aldehyde compound is added to adjust the particle size of the foaming agent, the particle size of the foaming agent is effectively reduced, the dispersibility of the AC foaming agent is improved, the product quality and the added value of the AC foaming agent are improved, and the economic benefit of the product is improved.
7. With the gas dispersion device of the present invention,
① the chlorine is distributed evenly, the flow speed of the chlorine in the inlet pipe is reduced after the chlorine is blocked by the bottom board and is dispersed into the chamber, the pressure of the gas can be homogenized initially in the chamber limited by the space of the chamber, then the gas is sprayed out through a plurality of small holes evenly distributed on the cover board, and the chlorine can be distributed evenly after the two times of distribution.
② the chlorine bubbles have uniform particle size, and the gas is sprayed from the top of the cover plate in uniform stream after passing through the gas disperser, and then dispersed into the liquid in the form of a plurality of small bubbles, i.e. the particle size of the bubbles can be well controlled.
③, the low pressure drop and the small resistance to gas outflow are achieved by the invention, which limits the inclination of the cover plate reasonably and ensures that the pressure loss of the gas flowing through the gas disperser is small.
Description of the drawings:
in order to more clearly illustrate the technical solution of the present invention, the drawings of the present invention will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and it is obvious to those skilled in the art that other drawings can be obtained based on the drawings without inventive labor.
FIG. 1 is a schematic sectional view of a spray reactor according to an embodiment of the present invention;
FIG. 2 is a schematic cross-sectional view of an oxidation reaction apparatus according to an embodiment of the present invention;
FIG. 3 is a schematic enlarged view of a portion of a gas disperser of a reactor according to an embodiment of the present invention;
FIG. 4 is a sectional plan view of a reaction vessel according to an embodiment of the present invention.
To further clarify the structure of the reaction vessel and the connection relationship between the respective components of the present invention, the following reference numerals are given and explained:
the method comprises the following steps of 1-liquid spraying device, 2-spray head, 3-spray pipe, 4-containing chamber, 5-slurry inlet, 6-auxiliary material inlet, 7-mixing chamber, 8-reaction kettle, 9-gas disperser, 10-impeller, 11-clutch, 12-driving device, 13-dropping pipe, 14-guide pipe, 91-air inlet pipe, 92-bottom plate, 93-side wall and 94-cover plate.
The technical scheme of the invention can be more clearly understood and explained by combining the embodiment of the invention through the reference sign description.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the invention, as detailed in the appended claims.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.
It is to be understood that although the terms first, second, third, etc. may be used herein to describe various information, these information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present invention. The word "if" as used herein may be interpreted as "at … …" or "when … …" or "in response to a determination", depending on the context.
The invention aims to provide a preparation method of an AC foaming agent, and the AC foaming agent prepared by the preparation method has uniform particle size and narrow particle size distribution range.
The object of the invention can be achieved by:
a preparation method of an AC foaming agent comprises the following steps:
(1) crushing the biurea raw material: filtering and washing the synthesized biurea, and performing superfine grinding on the biurea to obtain particles with the particle size of 4-8 mu m;
(2) preparation of biurea slurry: adding water into the crushed biurea to prepare a biurea slurry containing 20-40% of biurea, and then adding an oxidation auxiliary agent with the mass ratio of 0.3-10% of biurea;
(3) generating seed crystals: spraying the prepared 3-10% biurea slurry at a high speed through a liquid spraying device, entering the spraying reaction device from one inlet of the spraying reaction device, forming vacuum in the spraying reaction device, sucking chlorine gas into the spraying reaction device from the other inlet of the spraying reaction device, violently mixing the two in the spraying reaction device to instantly form a large amount of AC foaming agent crystal seeds, and collecting a reaction mixture with the AC foaming agent crystal seeds;
(4) mixing uniformly: adding the rest biurea slurry and the generated AC foaming agent seed crystal into a reaction kettle, adding a crystal form control agent, and uniformly mixing;
(5) adding an oxidant and continuing oxidizing until the reaction is finished;
(6) washing and drying: and after the reaction is finished, separating, washing and drying the slurry to obtain the finished product of the AC foaming agent.
Specifically, in the prior art, the synthesis of biurea is basically carried out in a reaction kettle, the particle size of the obtained biurea is basically between 40 and 160 μm, if the biurea enters a stage of producing an AC foaming agent by oxidation without treatment, the dissolution speed of the crude biurea in a solution is slow, and the dissolution speed is slow due to the inconsistent particle size and inconsistent reaction speed with an oxide, the particle size range of the obtained AC foaming agent product is wide and inconsistent, if the crude biurea is subjected to ultrafine treatment before reaction, the particle size of the treated biurea is small, the particle size uniformity is high, the dissolution rate is high, the overall reaction speed is high, the particle size of the AC foaming agent is easy to control, and the particle size distribution range is narrow, in the preparation method of the AC foaming agent provided by the invention, the chlorine gas is required to be crushed in advance before oxidizing the biurea, the specific surface area is increased, so that the dissolution speed of the biurea is high in the reaction process, the dissolving speed of the biurea is improved, thereby being beneficial to controlling the grain diameter of the AC foaming agent product.
Specifically, the biurea and the chlorine can be vigorously mixed by adopting the spray reaction device to react instantly to form a large amount of AC foaming agent crystal nuclei, the reaction time is short, the growth of crystals can be inhibited, and the biurea slurry is continuously sprayed out through the liquid spray device, so that the generated AC foaming agent crystal nuclei are uniform and stable.
Specifically, the AC foaming agent is added in advance as a seed crystal before the biurea is oxidized to prepare the AC foaming agent, then the oxidant is added to carry out the oxidation reaction of the biurea, the nucleation and the crystal growth of the AC foaming agent are carried out separately, the defects of wide particle size distribution, poor dispersibility and easy agglomeration of the AC foaming agent caused by different growth periods of the AC foaming agent can be avoided, and the AC foaming agent with narrow particle size range and uniform particle size can be obtained.
Specifically, the crystal form control agent is added to adjust the particle size of the AC foaming agent, and the finished product of the AC foaming agent is prevented from being granulated and agglomerated, so that the particle size of the AC foaming agent product is favorably controlled. When the crystal form control agent urotropine is used as an auxiliary agent in a chemical reaction process, solid particles can be effectively wrapped, and organic matters can have a dispersion characteristic, so that when biurea is oxidized by adopting an oxidant, the aldehyde compound is added to adjust the particle size of the foaming agent, the particle size of the foaming agent is effectively reduced, the dispersibility of the AC foaming agent is improved, the product quality and the added value of the AC foaming agent are improved, and the economic benefit of the product is improved.
Specifically, as shown in fig. 1, the spray reactor includes the following devices:
liquid injection apparatus 1, shower nozzle 2, injection pipe 3 and hold room 4, the export of shower nozzle 2 with 3 one end of injection pipe links to each other, the injection pipe 3 other end with hold room 4 and link to each other, shower nozzle 2 is equipped with thick liquids import 5 and auxiliary material import 6, smashes the biurea, adds the biurea thick liquids that water joined in marriage after the biurea passes through high-speed blowout of liquid injection apparatus 1, gets into shower nozzle 2 from thick liquids import 5, produces the negative pressure in the mixing chamber 5 this moment, and chlorine is inhaled shower nozzle 2 from auxiliary material import 6.
The biurea slurry and the chlorine are mixed vigorously at a throat between the mixing chamber 7 and the injection pipe 3, and react instantaneously to generate a large amount of AC foaming agent crystal nuclei, the crystal nuclei enter the accommodating chamber 4 from the injection pipe 6, and after the reaction is finished, an outlet below the accommodating chamber 4 is opened, and the generated AC foaming agent crystal nuclei and other reaction products are collected.
The conditions of production of ultrafine particles determine the particle morphology and particle size. Firstly, the dielectric constant of the reaction medium requires a sudden change; second, the reaction time is not preferably too long, because the short time can inhibit crystal growth. Thus, the rapid, continuous synthesis process provides AC blowing agent seeds of relatively narrow particle size distribution. Through the injection reaction device, a homogeneous system can be effectively maintained, the biurea slurry is sprayed out at a high speed through the liquid injection device 1, chlorine is violently mixed at a throat part between the mixing chamber 7 and the injection pipe 3, the aim of high-speed nucleation is achieved through instant reaction, the formed crystal nucleus has small particle size, and the distribution of particle size intervals is concentrated. Meanwhile, the speed of the liquid injection device 1 for injecting the biurea slurry can be controlled, so that the biurea slurry can be continuously injected, and the particle size of the produced AC foaming agent can be stable and adjustable.
Example 1
(1) Crushing the biurea raw material: filtering and washing the synthesized biurea, and performing superfine grinding on the biurea to obtain particles with the particle size of 4-8 mu m;
(2) preparation of biurea slurry: adding water into the crushed biurea to prepare a biurea slurry containing 20% of biurea, and then adding an oxidation auxiliary agent accounting for 5% of the mass of the biurea;
(3) generating seed crystals: spraying the prepared 10% biurea slurry at a high speed through a liquid spraying device, entering the spraying reaction device from one inlet of the spraying reaction device, forming vacuum in the spraying reaction device, sucking chlorine gas into the spraying reaction device from the other inlet of the spraying reaction device, violently mixing the two in the spraying reaction device to instantly form a large amount of AC foaming agent crystal seeds, and collecting a reaction mixture with the AC foaming agent crystal seeds;
(4) mixing uniformly: adding the rest biurea slurry and the generated AC foaming agent seed crystal into a reaction kettle, adding urotropine, and uniformly mixing;
(5) introducing chlorine gas until the reaction is finished, and controlling the flow of the chlorine gas at the early stage to be 0.8-1.2 m3The flow rate of chlorine gas in the middle period is 2.1-2.8 m3The flow rate of chlorine gas is 0.8-1.2 m in the later period3/min；
(6) Washing and drying: and after the reaction is finished, separating, washing and drying the slurry to obtain the finished product of the AC foaming agent.
Example 2
(1) Crushing the biurea raw material: filtering and washing the synthesized biurea, and performing superfine grinding on the biurea to obtain particles with the particle size of 4-8 mu m;
(2) preparation of biurea slurry: adding water into the crushed biurea to prepare biurea slurry containing 35% of biurea, and then adding an oxidation auxiliary agent accounting for 10% of the mass of the biurea;
(3) generating seed crystals: spraying the prepared 10% biurea slurry at a high speed through a liquid spraying device, entering the spraying reaction device from one inlet of the spraying reaction device, forming vacuum in the spraying reaction device, sucking chlorine gas into the spraying reaction device from the other inlet of the spraying reaction device, violently mixing the two in the spraying reaction device to instantly form a large amount of AC foaming agent crystal seeds, and collecting a reaction mixture with the AC foaming agent crystal seeds;
(4) mixing uniformly: adding the rest biurea slurry and the generated AC foaming agent seed crystal into a reaction kettle, adding urotropine, and uniformly mixing;
(5) introducing chlorine gas until the biurea is oxidized to 85% -95% of the total amount of reactants, then dripping hydrogen peroxide until the reaction is finished, and controlling the chlorine gas flow at the early stage to be 0.8-1.2 m3The flow rate of chlorine gas in the middle period is 2.1-2.8 m3The flow rate of chlorine gas is 0.8-1.2 m in the later period3/min；
(6) Washing and drying: and after the reaction is finished, separating, washing and drying the slurry to obtain the finished product of the AC foaming agent.
Specifically, chlorine oxidation is not easy to control the reaction end point, side reactions are easy to occur, by-product hydrochloric acid can be generated, the concentration of the hydrochloric acid is gradually increased along with the reaction, so that the color of a product is deep, the purity of the product is low, hydrogen peroxide is used in the later stage of the reaction, the reaction is changed from gas-liquid-solid three-phase reaction to liquid-solid two-phase reaction, the reaction is more sufficient, the reaction is mainly easy to control, the peroxidation phenomenon of an AC foaming agent after the reaction end point is reached is avoided, and the purity of a reaction product.
Example 3
(1) Crushing the biurea raw material: filtering and washing the synthesized biurea, and performing superfine grinding on the biurea to obtain particles with the particle size of 4-8 mu m;
(2) preparation of biurea slurry: adding water into the crushed biurea to prepare biurea slurry containing 35% of biurea, and then adding an oxidation auxiliary agent accounting for 8% of the mass ratio of the biurea;
(3) generating seed crystals: spraying the prepared 3% biurea slurry at a high speed through a liquid spraying device, entering the spraying reaction device from one inlet of the spraying reaction device, forming vacuum in the spraying reaction device, sucking chlorine gas into the spraying reaction device from the other inlet of the spraying reaction device, violently mixing the two in the spraying reaction device to instantly form a large amount of AC foaming agent crystal seeds, and collecting a reaction mixture with the AC foaming agent crystal seeds;
(4) mixing uniformly: adding the rest biurea slurry and the generated AC foaming agent seed crystal into a reaction kettle, adding urotropine, and uniformly mixing;
(5) simultaneously introducing chlorine and dropwise adding hydrogen peroxide, wherein the introduced chlorineThe mol ratio of the gas to the hydrogen peroxide is 1.2: 1, controlling the chlorine flow at the early stage to be 0.8-1.2 m3The flow rate of chlorine gas in the middle period is 2.1-2.8 m3The flow rate of chlorine gas is 0.8-1.2 m in the later period3And/min until the reaction is finished.
(6) Washing and drying: and after the reaction is finished, separating, washing and drying the slurry to obtain the finished product of the AC foaming agent.
Specifically, in the existing process for producing the AC foaming agent, chlorine is generally adopted for oxidation, the raw material of chlorine is easy to obtain and convenient to control, but the reaction of oxidizing biurea with chlorine can generate a large amount of hydrochloric acid as a byproduct, and the oxidation of biurea with hydrogen peroxide needs to be carried out in an acidic environment, and along with the oxidation reaction of hydrogen peroxide, the concentration of hydrochloric acid is reduced, the difficulty of later oxidation is increased, and the yield and purity of the product are low.
Example 4
(1) Crushing the biurea raw material: filtering and washing the synthesized biurea, and performing superfine grinding on the biurea to obtain particles with the particle size of 4-8 mu m;
(2) preparation of biurea slurry: adding water into the crushed biurea to prepare biurea slurry containing 40% of biurea, and then adding an oxidation auxiliary agent with the mass ratio of 0.3% of biurea;
(3) generating seed crystals: spraying the prepared 6.5% biurea slurry at a high speed through a liquid spraying device, entering the spraying reaction device from one inlet of the spraying reaction device, forming vacuum in the spraying reaction device, sucking chlorine gas into the spraying reaction device from the other inlet of the spraying reaction device, violently mixing the two in the spraying reaction device to instantly form a large amount of AC foaming agent crystal seeds, and collecting a reaction mixture with the AC foaming agent crystal seeds;
(4) mixing uniformly: adding the rest biurea slurry and the generated AC foaming agent seed crystal into a reaction kettle, adding urotropine, and uniformly mixing;
(5) simultaneously introducing chlorine and dropwise adding hydrogen peroxide, wherein the mole ratio of the introduced chlorine to the introduced hydrogen peroxide is 1.1: 1.05, and controlling the chlorine flow at the early stage to be 0.8-1.2 m3The flow rate of chlorine gas in the middle period is 2.1-2.8 m3The flow rate of chlorine gas is 0.8-1.2 m in the later period3And/min until the reaction is finished.
(6) Washing and drying: and after the reaction is finished, separating, washing and drying the slurry to obtain the finished product of the AC foaming agent.
Example 5
This example describes the reaction of a mixture of biurea slurry in an oxidation reaction unit with chlorine gas.
Wherein the steps (1) to (3) and the step (5) are the same as in example 5, and the step (4) is as follows:
(4) uniformly mixing: adding the rest biurea slurry and the generated AC foaming agent crystal seeds into an oxidation reaction device, and adding urotropine for uniformly mixing;
as shown in fig. 2 to 4, specifically, the oxidation reaction apparatus includes the following:
a reaction kettle 8, a gas disperser 9, an impeller 10, a clutch 11 and a driving device 12. The gas disperser 9 is arranged at the bottom of the reaction kettle 8, the driving device 12 and the centrifugal device 11 are arranged at the lower part of the reaction kettle, the driving device drives the impeller 10 and the gas disperser 9 to rotate, the gas inlet pipe 91 is arranged on the gas disperser 9, and the gas disperser 9 is composed of a bottom plate 92, a side wall 93 and a cover plate 94. The cover plate 94 has an annular air vent area with evenly distributed circular air vents.
The biurea slurry, the crystal form control agent urotropine and the AC foaming agent crystal nucleus enter the reaction kettle from a liquid inlet above the reaction kettle 8, and chlorine is introduced into the gas disperser 9 from the gas inlet pipe 91 after the uniform stirring. Chlorine gas overflows through small holes in the gas disperser 9 and enters the mixed solution to oxidize the biurea to generate the AC foaming agent.
A dropping liquid pipe 13 is further arranged above the reaction kettle 8, the dropping liquid pipe 13 can be opened, and hydrogen peroxide can be dripped into the reaction kettle 8 while chlorine is introduced into the reaction kettle 8.
Under the action of the driving device 7 and the clutch device 6, the gas disperser 9 rotates in the reaction kettle 8, which helps the gas to be dispersed in the mixed liquid more uniformly. The rotation can be clockwise and anticlockwise reciprocating motion, and the fluid motion can further break up bubbles, so that the chlorine gas is more uniformly dispersed.
The air inlet pipe 91 is provided with an impeller 10, and the impeller 10 is sleeved on the air inlet pipe 91 in an empty mode and can rotate axially. The impeller 10 can rotate at the same speed or at different speeds with the gas disperser 9 under the action of the clutch, and can also rotate at a low speed under the drive of fluid, and the rotation of the impeller 8 is favorable for dropwise adding hydrogen peroxide above the liquid level to diffuse in the liquid more quickly, and is favorable for complete reaction of biurea particles and hydrogen peroxide.
Furthermore, a flow guide pipe 14 is arranged on the side wall of the reaction kettle 8, and a motor is arranged to enable a part of liquid of the reaction kettle 8 to be pumped out from the bottom of the reaction kettle 8 and then enter the upper part of the reaction kettle 8, so that the material is further dispersed, the liquid in the reaction kettle 8 is good in distribution uniformity, the uniform particle size of the product is favorably controlled, and the particle size distribution range is narrowed.
The height H of said side wall 93 is not lower than 1/4 of the internal diameter D of the inlet pipe 91 in order to prevent a reduction in the flow area outside the inlet pipe 91, causing "pressure build-up". The cover plate 94 and the side wall 93 form an obtuse angle, so that the gas smoothly flows upwards after being blocked by the bottom plate 92 and the side wall 93, and the gas is uniformly sprayed out from the vent holes in the cover plate 94. The cover plate 94 has a circular area with uniformly formed vent holes that are circular. The total aeration area is 20-120% larger than the cross-sectional area of the gas inlet pipe 91, so as to properly reduce the flow rate of the fed chlorine gas, facilitate the uniform dispersion of the gas and also facilitate the reduction of the total pressure drop of the gas disperser 9. In order to properly reduce the flow rate of the gas, the uniform dispersion of the gas is facilitated, and the overall pressure drop of the distributor is also facilitated to be reduced. The vent hole is circular; the total area of the vent holes in the cover plate 94 is 1.1-2.5 times of the radial cross sectional area in the air inlet pipe 91. In order to fix the gas distributor 9, a reinforcing rib is further included, one end of the reinforcing rib is connected to the cover plate 94, and the other end of the reinforcing rib is fixed to the outer wall of the gas inlet pipe 91.
The collapse of large bubbles of gas in the liquid can result in vibration of the liquid and thus the entire container. When the gas flow rate is sufficiently high, the liquid turbulence is very severe and significant vibration of the vessel can occur. The reaction vessel 8 effectively eliminates vibration around the gas disperser 9. After passing through the gas disperser 9, the gas is sprayed out from the top of the distribution cover plate in a uniform thin flow, and then is dispersed into the liquid in the form of a plurality of small bubbles, namely the particle size of the bubbles can be well controlled. Since frequent generation and collapse of large bubbles does not occur, no significant vibration of the gas disperser 9 and the surrounding liquid occurs.
Comparative example 1
A preparation method of an AC foaming agent comprises the following steps:
(1) preparation of biurea slurry: adding water into the synthesized biurea to prepare biurea slurry containing 40 wt% of biurea, and then adding an oxidation auxiliary agent which is bromide or iodide and accounts for 10 wt% of the biurea;
(2) complete oxidation: putting the biurea slurry into a reaction kettle, introducing chlorine into the reaction kettle until the reaction is finished, and controlling the flow of the chlorine gas at the early stage to be 0.8-1.2 m3The flow rate of chlorine gas in the middle period is 2.1-2.8 m3The flow rate of chlorine gas is 0.8-1.2 m in the later period3/min；
(3) Washing and drying: and after the reaction is finished, separating, washing and drying the slurry to obtain the finished product of the AC foaming agent.
Comparative example 2
A preparation method of an AC foaming agent comprises the following steps:
(1) crushing the biurea raw material; filtering and washing the synthesized biurea, and performing superfine grinding on the biurea to obtain particles with the particle size of 4-8 mu m;
(2) preparation of biurea slurry: adding water into the crushed biurea to prepare biurea slurry containing 40 wt% of biurea, and then adding an oxidation auxiliary agent which is bromide or iodide and accounts for 10 wt% of the biurea;
(3) complete oxidation: putting the biurea slurry into a reaction kettle, introducing chlorine into the reaction kettle until the reaction is finished, and controlling the flow of the chlorine gas at the early stage to be 0.8-1.2 m3The flow rate of chlorine gas in the middle period is 2.1-2.8 m3The flow rate of chlorine gas is 0.8-1.2 m in the later period3/min。
(4) Washing and drying: and after the reaction is finished, separating, washing and drying the slurry to obtain the finished product of the AC foaming agent.
Comparative example 3
A preparation method of an AC foaming agent comprises the following steps:
(1) crushing the biurea raw material; filtering and washing the synthesized biurea, and performing superfine grinding on the biurea to obtain particles with the particle size of 4-8 mu m;
(2) preparation of biurea slurry: adding water into the crushed biurea to prepare biurea slurry containing 40 wt% of biurea, and then adding an oxidation auxiliary agent which is bromide or iodide and accounts for 10 wt% of the biurea;
(3) adding a crystal form control agent: adding the biurea slurry into a reaction kettle, adding a crystal form control agent, and uniformly mixing, wherein the crystal form control agent is urotropine, and the content of the urotropine in liquid is 1.0 g/L;
(4) complete oxidation: introducing chlorine into the reaction kettle until the reaction is finished, and controlling the flow of the chlorine gas at the early stage to be 0.8-1.2 m3The flow rate of chlorine gas in the middle period is 2.1-2.8 m3The flow rate of chlorine gas is 0.8-1.2 m in the later period3/min。
(5) Washing and drying: and after the reaction is finished, separating, washing and drying the slurry to obtain the finished product of the AC foaming agent.
The particle size of the AC foaming agent product obtained from the above 8 sets of tests was measured using a malvern laser particle size tester, and the following data were obtained:
from comparison of experimental data of comparative examples 1 to 3 and example 1, it can be seen that the method of preparing seed crystals using the liquid ejecting apparatus described in example 1 is advantageous in controlling uniformity of particle size of the AC foaming agent and narrowing a particle size distribution range of the AC foaming agent.
Furthermore, the comparison of experimental data of comparative examples 1 to 3 shows that the crushing of the biurea raw material and the addition of the crystal form control agent urotropine also play a role in controlling the uniformity of the particle size of the AC foaming agent and narrowing the particle size distribution range of the AC foaming agent.
From the comparison of the experimental data of example 2 and example 1, it can be seen that the method of generating the AC foaming agent by two-stage composite oxidation is beneficial to control the uniformity of the particle size of the AC foaming agent and narrow the particle size distribution range of the AC foaming agent.
From comparison of experimental data of examples 3 to 4 and example 2, it can be seen that the method of simultaneously oxidizing biurea with chlorine and hydrogen peroxide to generate the AC foaming agent is beneficial to control of uniformity of particle size of the AC foaming agent and narrow particle size distribution range of the AC foaming agent.
From the comparison of the experimental data of examples 3 to 4 and example 5, it can be seen that the use of the redox device according to the present invention is advantageous in controlling the uniformity of the particle size of the AC foaming agent and narrowing the particle size distribution range of the AC foaming agent.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A preparation method of an AC foaming agent is characterized by comprising the following steps:
(1) crushing the biurea raw material: filtering and washing the synthesized biurea, and performing superfine grinding on the biurea to obtain particles with the particle size of 4-8 mu m;
(2) preparation of biurea slurry: adding water into the crushed biurea to prepare a biurea slurry containing 20-40% of biurea, and then adding an oxidation auxiliary agent with the mass ratio of 0.3-10% of biurea;
(3) generating seed crystals: spraying 3% -10% of prepared biurea slurry at a high speed through a liquid spraying device (1), feeding the slurry into a spraying reaction device from a slurry inlet (5), forming vacuum in the spraying reaction device, sucking chlorine gas into the spraying reaction device from an auxiliary material inlet (6) of the spraying reaction device, violently mixing the slurry and the auxiliary material in the spraying reaction device to instantly form a large amount of AC foaming agent crystal seeds, and collecting a reaction mixture with the AC foaming agent crystal seeds;
(4) mixing uniformly: adding the rest biurea slurry and the generated AC foaming agent seed crystal into a reaction kettle (8) provided with a gas disperser (9), adding a crystal form control agent, and uniformly mixing;
(5) adding an oxidant and continuing oxidizing until the reaction is finished;
(6) washing and drying: and after the reaction is finished, separating, washing and drying the slurry to obtain the finished product of the AC foaming agent.
2. The method for preparing an AC foaming agent according to claim 1, wherein the oxidizing agent in the step (5) is chlorine gas, and the flow rate of the chlorine gas at the front stage is controlled to be 0.8-1.2 m3The flow rate of chlorine gas in the middle period is 2.1-2.8 m3The flow rate of chlorine gas is 0.8-1.2 m in the later period3/min。
3. The method of claim 1, wherein said oxidizing agent in step (5) is hydrogen peroxide and chlorine.
4. The process for the preparation of an AC blowing agent according to claim 3, characterized in that said step (5) comprises in particular the steps of: introducing chlorine gas into the reaction kettle to reach 85% -95% of theoretical chlorine flow, dropwise adding hydrogen peroxide to continue oxidizing until the reaction is finished, and controlling the early chlorine flow to be 0.8-1.2 m3The flow rate of chlorine gas in the middle period is 2.1-2.8 m3The flow rate of chlorine gas is 0.8-1.2 m in the later period3/min。
5. The process for the preparation of an AC blowing agent according to claim 3, characterized in that said step (5) comprises in particular the steps of:
and simultaneously introducing chlorine and dropwise adding hydrogen peroxide until the reaction is finished, wherein the mole ratio of the introduced chlorine to the hydrogen peroxide is (1.1-1.2): (1-1.05) and the chlorine flow rate at the early stage is controlled to be 0.8-1.2 m3The flow rate of chlorine gas in the middle period is 2.1-2.8 m3The flow rate of chlorine gas is 0.8-1.2 m in the later period3/min。
6. The method for preparing an AC foaming agent according to claim 1, wherein the crystal form control agent is urotropin.
7. The method of preparing an AC blowing agent according to claim 1, characterized in that: the gas disperser (9) comprises a gas inlet pipe (91), a bottom plate (92), a side wall (93) and a cover plate (94); the bottom plate (92), the side wall (93) and the cover plate (94) are fixedly connected to form a chamber; one end of the air inlet pipe (91) is communicated with the cover plate (94); the cover plate (94) is conical, and vent holes are uniformly formed in the cover plate (94).
8. The method of claim 7, wherein an included angle α is formed between the cover plate (94) and the side wall (93), and the size of the α is 90-120 °.
9. The method for preparing an AC foaming agent according to claim 7, wherein an impeller (8) is sleeved on the air inlet pipe (91) in a hollow manner, the impeller (8) can rotate radially, and a clutch is arranged at the bottom of the reaction tank (2) and can enable the impeller (8) and the gas disperser (9) to rotate in a differential speed manner.
10. The preparation method of the AC foaming agent according to claim 1, wherein the injection reaction device is provided with a nozzle (2), an injection pipe (3) and a containing chamber (4), an outlet of the nozzle (2) is connected with one end of the injection pipe (3), the other end of the injection pipe (3) is connected with the containing chamber (4), the nozzle (2) is provided with two inlets, the biurea slurry enters the nozzle (2) from a slurry inlet (5), and the oxidant enters the nozzle (2) from an auxiliary material inlet (6).
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